1. Field
The present disclosure generally relates to composite structures, and deals more particularly with a bonded and tailorable composite assembly, such as an aircraft empennage.
2. Background
Composite materials have been integrated into airfoil designs in recent years in order to reduce aircraft weight. For example, airfoils such as vertical and horizontal stabilizers have been designed with an outer composite laminate skin. However, due to design limitations, interior structural components of these stabilizers, such as spars, stringers and chords, are predominantly fabricated from metal such as aluminum or titanium, all secured together with metal fasteners. These metal components add undesired weight to the aircraft, and are both time consuming and labor intensive to fabricate and assemble. In order to decrease aircraft weight and increase fuel savings, a greater use of lightweight materials such as bonded, rather than fastened composites is required, however known designs have limitations that make replacement of metal components with composites challenging. Moreover, these limitations make it difficult to obtain certification of components and subassemblies by certification authorities.
In addition to the problems discussed above, vertical and horizontal stabilizer designs that rely on extensive use of metal components are not easily tailored to optimize a combination of flight characteristics, such as lift, bending and torsional stiffness, and discrete damage containment/arrestment. Also, the use of many separate spars and/or chords in these stabilizer designs may make it difficult to optimize load transfer from the outer skins. Further, known stabilizers having control surfaces such as elevators and rudders often require the incorporation of flutter pumps or reactive masses that are connected to the control surfaces in order to control aeroelastic stability commonly referred to as flutter. The use of these flutter control devices adds undesired weight and complexity to the aircraft.
Accordingly, there is a need for a composite assembly such as an aircraft empennage having unitized and bonded, all composite vertical and horizontal stabilizers that substantially reduce or eliminate the need for metal components, including fasteners, and eliminate the need for flutter control devices. There is also a need for a more efficient empennage with vertical and horizontal stabilizers having composite outer skins with individually tailored interlaminar fracture toughnesses as well as stiffnesses, and an integrated all-composite grid understructure structure that permits tailoring the stabilizers to optimize flight characteristics, service life durability and failsafe reliability.